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THE ADVANTAGE OF LOW GROWTH TEMPERATURE AND V/III RATIO FOR In_xGa_(1-x)As NANOWIRES GROWTH
EDY WIBOWO,ZULKAFLI OTHAMAN,SAMSUDI SAKRANI,IMAM SUMPONO 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.2
Cylindrical In_xGa_(1-x)As nanowires (NWs) perpendicular to the substrate have been successfully grown using MOCVD. Morphology of In_xGa_(1-x)As NWs has been observed using Field Emission-Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). Both FE-SEM and TEM results show that the NWs grown at low growth temperature and V/III ratio were via direct impinging mechanism. Energy Dispersive X-ray spectroscopy (EDX) results confirm that the cylindrical NWs grown via direct impinging mechanism and tends to have uniform chemical composition.
AFM, HR-XRD AND PL CHARACTERIZATION OF STACKED STRUCTURES In0.5Ga0.5As/GaAs QUANTUM DOTS
DIDIK ARYANTO,ZULKAFLI OTHAMAN,AMIRA S. AMERUDDIN,ABD. KHAMIM ISMAIL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.2
In0.5Ga0.5As quantum dots (QDs) stacked structure were studied using atomic force microscopy (AFM), high-resolution X-ray diffraction (HR-XRD) and photoluminescence (PL) characterization. Evolution in the dots size and dots density in the stacked structures is strongly influenced by the dot formation in the under-layer and the structure of the spacer layers. AFM results revealed that the dots formation on the top can be changed by increasing the number of stacked QDs. However, the dots formation is not vertically aligned since HR-XRD measurement gave different satellite peak on n-stacked QD structures. Room-temperature PL measurements show variation in the PL spectra, where blue-shifted PL peak positions are observed when the number of stack is increased. Variation in the HR-XRD and PL measurement is also attributed to the size, composition and density of the dots in the stacked structures.
DIDIK ARYANTO,ZULKAFLI OTHAMAN,ABD. KHAMIM ISMAIL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.2
The effect of a thin In_(0.1)Ga_(0.9)As underlying layer on the structural properties of single layer In_(0.5_Ga_(0.5_As quantum dots (QDs) was investigated using atomic force microscopy (AFM), transmission electron microscopy (TEM) and high-resolution X-ray diffraction (HR-XRD) characterization. The size of dots formed on the surface is uniform but the density increases with the addition of In_(0.1_Ga_(0.9)As underlying between In_(0.5)Ga_(0.5)As QDs and GaAs buffer layer. This is consistent with the TEM characterization. The existence of thin underlying layer has caused the dots to have different crystal orientation as shown in TEM characterization. From the HR-XRD characterization, broad peak of In0.1Ga0.9As underlying layer and QDs has been observed. The wider width of the layer peak than the expected one has been attributed to the strain-relaxation-induced defects. The growth of a thin In_(0.1)Ga_(0.9)As underlying layer in the In_(0.5)Ga_(0.5)As/GaAs structures strongly affects the structural properties, which was also believed to influence the optical properties of QDs.
Shumaila Islam,Rosly Rahman,ZULKAFLI OTHAMAN,Saira Riaz,Shahzad Naseem 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6
Films of multi-organic indicators, encapsulated in silica–titania hybrid matrix with CTAB, have beensynthesized using sol–gel dip coating method. Two types of stable,dense and uniform matrices wereannealed at a 150 ℃ within two time intervals 1 h and 2 h by using 0.1 M and 0.5 M indicatorconcentrations. Nanoparticles are uniformly distributed with size in the range from 15–28 nm. Matriceshave high surface area (418.18–441.30 m2/g), which has more capability to sense the broader pH range. Spectroscopic studies showed the establishment of heterogeneous chemical bonding which indicative ofstability of matrices with 69% porosity. The response of the sensor is optimum at pH 9.
Synthesis and characterization of multilayered sol–gel based plastic-clad fiber optic pH sensor
Shumaila Islam,Rosly Abdul Rahman,Zulkafli Bin Othaman,Saira Riaz,Shahzad Naseem 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.23 No.-
The fabrication and characterization of an optical fiber pH sensor for the detection range 3–11 are described. The sensing element consists of a combination of indicators encapsulated in mesoporous surfactant based hybrid matrix, which are deposited onto an uncladed plastic optical fiber. Stable, dense and uniform sol–gel cladding with more than 90% transparency in the visible range are observed. Roughness value 9.7–6.57 nm is obtained by AFM. Film thickness, refractive index, and porosity are found to vary with number of coatings, 70% porosity is determined with 116 nm thickness. The response of the sensor with third layer is observed in acid and basic medium.